Advanced Exergy Analysis of GT-sCO2 Combined Cycle

Abstract

The use of the supercritical carbon dioxide Brayton cycle (SCBC) for waste heat recovery from the gas turbine cycle (GTC) can enhance system performance and reduce CO2 emissions. To analyze the possibility of component optimization and the characteristics of the exergy destruction, a model of a gas turbine-supercritical carbon dioxide (GT-sCO2) combined system with a triple cascade layout has been established, and the exergy destruction of the GT-sCO2 combined system has been analyzed for the first time using an advanced exergy analysis based on a conventional exergy analysis, which further classified the exergy destruction into endogenous, exogenous, avoidable, and unavoidable, and pointed out the direction for the optimization of the new system. The results reveal that the GTC subsystem has larger destruction than the SCBC subsystem. The endogenous exergy destruction ratio of the GT-sCO2 combined cycle is 88.86%, while the endogenous avoidable part is 20.94%. The combustion chamber has the largest endogenous avoidable exergy destruction in the GTC subsystem (51.42 MW), while the sCO2 compressor has the largest endogenous avoidable exergy destruction in the SCBC subsystem (1.89 MW). Depending on the endogenous avoidable exergy destruction, the order of optimization of components is: combustion chamber, gas turbine, air compressor, sCO2 compressor, high-temperature sCO2 turbine, cooler, high-temperature recuperator, low-temperature sCO2 turbine, and low-temperature recuperator, and the corresponding component improvement suggestions are made to aid in subsequent optimization efforts.